Poromeric (poroplastic) articles are made with microporous sheet material such as "CORFAM" of the E. I. duPont Company, "AZTRAN" of the B. F. Goodrich Company, "GENAIRE" of the General Tire Company, "XYLEE" from West Germany and "CLARINO" from Japan. The microporous poromeric sheet material may be made in a variety of ways, and with a variety of polymers, notably polyvinylchloride and polyurethane. None of these methods is sufficiently known in the art because of the fact that published patents and literature either do not disclose enough, or are lacking, or are shrouded in trade secrecy. In each case where an article of raiment, notably shoes, was fabricated from such poromeric sheet material, a compromise had to be made between comfort and mechanical strength. These compromises proved to be incorrect and the first four poromerics mentioned above were withdrawn from the market at a loss estimated at over 200 million dollars.
One of the contributing factors to the commercial demise of the duPont material for shoes was leakage at the seams particularly at the juncture of the upper and the sole. (See Chemistry and Industry, Dec. 10, 1966, page 2084).
However, two methods of manufacturing poromeric sheet material are clearly known, one method being described in U.S. Pat. No. 3,353,981 and the other method in U.S. Pat. No. 3,718,561. The present invention is an improvement on the latter inventions.
The problem which the present invention has solved, is the problem of comfort versus mechanical strength, by providing both, instead of one at the expense of the other. Both attributes co-exist in the sheet material of the present invention. Comfort is provided where needed, and this is generally for the largest part of the area of the poromeric article, and mechanical strength is provided where needed, and this is generally in the area where the greatest flex-life is desired such as the welt-area of a shoe where the upper is attached to the sole.
In outerwear the area of mechanical strength and maximum waterproofness is provided near the shoulder sections. In upholstery the area of mechanical strength is provided at the seaming sections and also at the edge portions of seats where maximum abrasive wear takes place. Thus according to my invention microporosity is retained for maximum comfort, breathability, and moisture vapor transmission yet flex-life, abrasion resistance, stitch-strength, are provided in the relatively minor areas of the microporous article where these functional attributes are necessary.
Thus a poromeric article which is torn between the Scylla and Charybdis of comfort versus mechanical strength, is now possible to manufacture having both comfort and mechanical strength, exactly as and where needed, by the process of de-poromerizing the material in desired areas. The de-poromerizing areas have the near-maximum mechanical properties of a solid mass which has not been attenuated by micro-pores therein.